This invention relates to an inhalation apparatus for dispensing substances for inhalation and, in particular, but not exclusively, for dispensing medicinal products in aerosol form from a pressurised dispensing container.
It is known to provide a sensor in an inhalation apparatus to detect inhalation by the user in order to synchronise with inhalation the release into the inhaled air flow of the substance to be inhaled. It is, for example, important in the administration of aerosol products for the relief of asthma that the timing of the dispensing operation should be carefully controlled to ensure maximum deposition of substance in the user""s lungs.
It is known from GB 2266466 to provide an electrically operated dispensing means responsive to a signal generated by a sensor which is responsive to a flow of air through the passageway. The disadvantage of this solution is that the apparatus is expensive.
An object of the present invention is to provide dispensing means in which mechanical means are used to co-ordinate the release of the substance with the inhalation.
The present invention therefore provides an inhalation apparatus for dispensing a product comprising a housing and an end cap axially slidable relative to the housing, said housing comprising a position adapted to receive a pressurized dispensing container and being connected to the mouthpiece, and a duct communicating with the container receiving portion for conveyance of product towards the mouthpiece; said end cap comprising a portion for engaging the pressurized dispensing container; one of said end cap and housing comprising an inwardly directed rim; the other of said end cap and housing including an outwardly directed flange which fits within said rim; said end cap being movable between a first position in which said rim and flange have an axial overlap and there is no or a minimal flow of air through said housing and a second position in which there is a maximum flow of air, the air flow being created by a user applying suction to the mouthpiece.
An advantage of the present invention is that the dispensation of the medicament is synchronised with inhalation of the user using an inexpensive inhalation apparatus.
Preferably said end cap is movable to a third position, the movement of the end cap between the second and third position s providing means for the dispensing of the product into the maximum air flow and for delaying the discharge of the product until the maximum air flow has been established.
Preferably the end cap comprises the inwardly directed rim and the housing comprises the outwardly directed flange.
Alternatively the housing comprises the inwardly directed rim and the end cap comprises the outwardly directed flange.
Preferably the end cap comprises a collar comprising the inwardly directed rim and a plurality of axial ribs on an internal surface of the collar, said rim and ribs, with the end cap in the first position, forming a close fit with the outwardly directed flange of the housing so that there is no or a minimum air flow through the housing, an end of the axial ribs furthest from the rim comprising position stops for contacting the rim when the end cap is in the third position to prevent axial movement of the rim beyond the stops; the collar further comprising circumferential recesses between the ribs such that with the end cap in the second or third positions, the maximum air flow can pass through the circumferential recesses between the housing and the collar when a user applies suction to the mouthpiece.
Alternatively the housing comprises a collar comprising the inwardly directed rim and a plurality of axial ribs on an internal surface of the collar, said rim and ribs, with the end cap in the first position, forming a close fit with the outwardly directed flange of the end cap so that there is no or a minimum air flow through the housing, an end of the axial ribs furthest from the rim comprising position stops for contacting the rim when the end cap is in the third position to prevent axial movement of the rim beyond the stops; the collar further comprising circumferential recesses between the ribs such that with the end cap in the second or third positions, the maximum air flow can pass through the circumferential recesses between the housing and the collar when a user applies suction to the mouthpiece.
Preferably the minimum air flow is provided by a bleed hole in the housing.
Alternatively the minimum air flow is provided by a bleed hole in the end cap.
An advantage of providing a bleed hole is that a minimum air flow is provided when suction is applied to the mouthpiece even when the apparatus is in the rest state with the rim and flange having an axial overlap. This prevents the user of the inhalation apparatus panicking by being unable to inhale a quantity of air.
Preferably the ratio of the maximum volume flow rate of air to the minimum volume flow rate of air lies in the range 8 to 12.
Preferably the ratio of the maximum volume flow rate of air to the minimum volume flow rate of air is approximately 10.
Preferably the end cap is biased in use into the first position by means of the pressurised dispensing container.
An advantage of the present invention is that the apparatus does not require a separate spring component in order to operate. This helps to reduce the manufacturing and assembly costs of the apparatus.